Return speech control



Sept. 22, 1936. J. A. FRAzlER RETURN SPEECH CONTROL Filed Jan. 8, 1934 3Sheets-Sheet l IN V EN TOR.

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RETURN SPEECH CONTROL Sept. 22, 1936.

Sept, 22, 1936. J. A. FRAzlER RETURN SPEECH CONTROL I5 Sheets-Sheet 3Filed Jan. 8, 1934 un? ulm, Qms Q lkw INVENToR.

. F azr Patented Sept. 22, 1936 `Tj UNITED sTATEs PATENT OFFICE 2Claims.

This invention relates to electrical sound transmission systems and moreparticularly to a system embodying the use of novel circuits, switchesand arrangement, of parts whereby sound may be electrically transmittedin both directions in the system at the pleasure of the person utilizingthe novel controls of the system.

It is an object of the invention to provide for selective control of thetransmitting and receiving stations. f

A further object of the invention is the provision of novel switchingarrangements wherebyl the system is greatly simplified and thereforeeasier and less expensive to manufacture.

Another object is the provision, in a monitoring system,V of controldevices whereby a control operator may have at all times absolutesupervision of all receiving stations.

Other objects and advantages will appear in the following specificationand the novel features ofthe invention will be particularly pointed outin the appended claims.

The development of electrical sound transmission systems and monitoringcircuits has failed to provide a system allowing two directionaltransmission selectively controllable. The present invention isadaptable to the use of schools and other institutions where silentsupervision and return speech control would be an impetus to efflciency.

The invention/is illustrated in the accompanying drawings, forming partof this application, in

which:

Figure l is a schematicdrawing illustrating my invention as utilized inconnection with public address systems and embodying `monitor speakerand microphone controls;

Figure 2 is a View similar to that shown in Figure l, but illustrating amodification thereof, whereby a radio power detector and a phonographpick up may be selectively utilized; and

Figure 3 is a View similar to those above described but illustrating afurther modification of the invention, wherein the control operator may'selectivelyy listen in to one of the receiving stations while notinterfering in any manner with reception at the remaining stations.-This modification also illustrates the use of separate amplification inthe sending and receiving stations.

Referring to the drawings, which are common in the respect that thegroups of loudspeakers illustrated therein are symbolic of speakers indifferent rooms, the number of rooms capable of being served beinglimited only by the capacity of the amplification units. It is, ofcourse, to be understood that all of the various switches hereinutilized are to be so placed as to centralize the control of the entiresystem.

In Figure l, the control mechanism consists of one, double pole, doublethrow, toggle switch and one single pole, single throw toggle switch somounted as to operate simultaneously.

'Ihe invention may be readily understood from a perusal of the followingdescription taken in connection with the accompanying drawings and inFigure 1 the invention has been illustrated as used in connection with apublic address system and is shown as being provided with a monitorspeaker and microphone both provided with switches.

The operation of the system disclosed in Figure 1 is as follows:

When the control switch is ln the position indicated at A", the mainline to the outside speakers is connected to the amplifier input. Atthis vtime the circuit to the microphone is open.

When the control switch is placed in the position indicated at B, themonitor speaker is disconnected, the main line to the outside speakersis connected to the amplier output and the circuit to the originalmicrophone is closed.

This system accomplishes the following results:` When the control switchis thrown to position A all of the room loudspeakers or outside speakersare connected to the amplifier input and serve as microphones only, todetect sounds throughout the rooms wherein they are located andreproduce them by means of the monitor speaker for the control operator.When the control is in position B, the room loudspeakers are on amplieroutput and serve as loudspeakers only.

The purpose of this system is to permit school superintendents andothers operating the centralized control to have instantaneous two-waycommunication by switch selection with the various rooms wherein thespeakers are located. The system also permits the selective listening into various class room activities thereby conserving the time heretoforeutilized in the personal supervision of class room activities. By theuse of this 50 reverse amplification system, the same high gainamplification may be employed with room loudspeakers while they areserving as microphones as is used in the standard desk microphoneutilized in all public address systems. By using a single unit to serveboth as a loudspeaker and as a microphone, all danger of feed back fromclose proximity of microphone and speaker is entirely eliminated.

It is to be noted that no additional amplification is needed when theroom speakers are used as microphones and that but a single switch isnecessary for the speaker located in any one room, since the controlswitch disconnects the entire line from the input and connects it withthe output of the amplifier.

The speaker microphones utilized in this invention are magnetic,permanent magnetic field dynamic or electro dynamic speakers whenequipped with proper filtering devices in their field supplies.

In Figure 2, there is shown a system having all the qualities of thesystem above described but modified by the provision of a simplifiedarrangement of switches whereby radio, phonograph or microphoneconnections may selectively be made in addition to the control of thespeakers as outlined in the description of the system disclosed inFigure 1.

The switching arrangement consists, as illustrated in the drawings, ofone double pole double throw, three position switch J; one triple pole,double throw, three position switch K and a plurality of simple switchesfor the various room speakers.

When the switch J is in position A, the monitor speaker is connected tothe amplifier output and the main line controlling all of the roomloudspeakers is connected to the amplifier input and at this time theloudspeakers are serving as microphones. When the switch J is in theposition indicated at B", no connections are made thereby. When in theposition indicated at C, the monitor speaker is connected to theamplifier input and serves as a microphone and the main line feeding theroom speakers is connected to the amplifier output. Therefore, thefunctions of the amplifier with the control switch at position C" arethe reverse of those with the switch at position "A.

In order for the switch J to function, it is necessary to first placeswitch K in neutral position and likewise, the switch J should be placedin neutral position when it is desired to operate switch K.

When the switch K is in the position indicated at D a phonograph isconnected to the amplifier input and both the monitor speaker and themain line feeding the room speakers are connected to the amplifieroutput. When switch K is in the position indicated at E, no connectionsare made. When in the position indicated at F, a radio receiver powerdetector output is connected to the amplifier input and the monitorspeaker and main line feeding the room speakers are connected to theamplifier output.

From the above, it will be noted that this system is similar to thatdisclosed in Figure 1, but that the necessity of a desk microphone andmicrophone transformer have been eliminated.

In Figure 3, there is disclosed a still further modification and theparticular embodiment shown in the drawings shows the system connectedto a standard public address system.

The amplifier, in its preferred form, in this instance is of the threestage type of high gain and is connected directly by means of exiblewires or l the like to the two contacts of a rotary switch arm C, thecontacts being insulated one from the other.

When the arm is rotated, the contacts make direct connection with linepoints D, E, F and G, so that the corresponding room loudspeakers I, 2,3 and 4 are connected directly to the input of the return speechamplifier.

When the public address system is connected to al1 of the room speakers,through individual switches zc, the contact arm C must be set in aneutral position.

A monitor speaker M is connected to the arm contacts of a double pole,double throw switch B.

When thrown to the position indicated at K, the monitor speaker isconnected to the output of an amplifier PA in order to monitor programstransmitted over the public address system. When thrown to the positionindicated at L, the monftor speaker is connected directly to the outputof a return speech amplifier RS and must remain in this position whilethe operator is listening to sounds picked up by room loud speakers l,2, 3 or 4 as selected by the rotary switch C through the contacts D, E,F or G.

It will be noted that the system last described differs from theforegoing two modifications in that the operator may transmit radio,phonograph or public address system transmissions through the amplifierPA to the room loud speaker 4, for example, while disconnecting allremaining a: switches except that one controlling speaker 4 and by thenthrowing switch B to position L may listen to the activities in theroomshaving the speakers l, 2 and 3 'as selected through switch C.

While three forms of the invention have been shown and described herein,it will be apparent to those skilled in the art that the invention isnot so limited but that various minor changes may be made thereinwithout departing from the spirit thereof or the scope of the appendedclaims.

What is claimed is:

1. In a program distribution system, a plurality of independentdistributing channels, a r imbined microphone transmitter and loudspeaker receiver associated with each of said channels, an amplifier, aninput circuit for the amplifier, switch means for selectively connectingthe amplifier input circuit to each of the combined microphonetransmitters and loud speaker receivers, and an output circuit for saidamplifier, a monitoring receiver and transmitting microphone, a secondamplifier being connected to a pick-up of sound transmission ,from anoutside source, an output circuit for the second amplifier being incircuit with the combined microphone transmitters and loud speakerreceivers, a second output circuit associated with the said secondamplifier, and said monitoring receiver and transmitting microphonehaving switch means, and the said switch means adapted to connect themonitor with the first mentioned amplifier to perform as a receiver, orto connect the monitor with the second mentioned amplifier to perform asa microphone.

2. In a program system, a plurality of independent distributionchannels, a combined microphone transmitter and loud speaker receiverassociated with each of' said channels, an amplifier, an input circuitfor the amplifier, switch means for selectively connecting the amplifierinput circuit to each of the combined microphone transmitters and loudspeaker receivers. and an. output circuit for said axnpiier,` amonitoring re ceiver and transmitting microphone, al second amplifierbeing connected tow. pick-up of sound transmission from an outsidesource, an output circuit for the second ampliiier being in circuit withthe combined loud speaker receivers and microphone transmitters, switchmeans in the output circuit of the second amplifier adapted to connecteither one or all of the combined loud speaker receivers and microphonetrnnsmitters,

with the pick-up of sound transmissionirom an outside source, a secondoutput circuit associated with the said second amplifier, the saidmonitoring receiver and transmitting microphone having switch means, andthe said switch means adapted to connect the monitor with the rstmentioned amplifier to perform as a receiver, or to connect the monitorswitch with the second mentioned ampliiier to perform as a microphone.

' JOHN A. FRAZIER.

